[Every other week, Gamasutra examines the most popular Facebook games according to monthly active users, looking at the top titles and developers on the social network to see who's attracting or losing players.] After an initial flourishing period during which it added millions to its user count every week and shot up Facebook's app leaderboard, Zynga's Hidden Chronicles has finally seen its growth stall -- the game has 33.1 million monthly active users, around the same amount it had the last week. It's still the third most popular game on Facebook, though, and the hidden object game managed to reach that spot in just two months after its launch -- something other developers are sure to notice. Disney/Playdom actually launched another hidden object title last week with Blackwood and Bell Mysteries. Ahead of Hidden Chronicles on the App Leaderboard are two other Zynga titles, CityVille and Texas HoldEm Poker. CityVille has 46.9 million monthly users, which is down from the 47.2 million it had two weeks ago. Texas HoldEm Poker, meanwhile, gained half a million users and now has 33.5 million. In number 4 and 5 on the App Leaderboard are two more Zynga releases, CastleVille and FarmVille, respectively. CastleVille lost nearly a million users in the past two weeks and now has 28.8 million, while FarmVille's audience has remained stable at 28.4 million. Electronic Arts/Playfish's The Sims Social at #6 has 300,000 fewer players and a 20.6 million total. It's followed by Zynga's Words With Friends with 400,000 new users and a 20.4 million total, and Wooga's Diamond Dash with 2.1 million new players and a 17.6 million total. And closing out the App Leaderboard's top ten list, King.com's Bubble Witch Saga (1.5 million new users over the last two weeks) and Zynga's Empires & Allies (300,000 fewer users) both have 15.4 million monthly active players. You can see the full list of the top 20 Facebook games along with exact monthly active user counts below: All charts and data are courtesy of Facebook application metrics and trends site AppData.